There exists a need in the industry for reduced area image reading devices that can be used in industrial application including bar code readers, PDA's and even wireless/cellular picture phones. With the ever-decreasing size of these applications, miniaturization of the image reading module itself is a perennial problem.
Present packaging techniques are often not adequate for the rate of miniaturization currently required in the industry. Another problem with current packaging techniques is a lack of a suitable device testing points, which could be used instead of the device's interconnect ribbons at the verification and calibration stage of the manufacturing process. These ribbons become worn and often need replacing before final shipping.
US Patent Application Publication 2003/0089776 filed on Mar. 7, 2002 by Henick and published on May 15, 2003, discloses a packaging technique for an image reader module, which uses support posts to connect the boards and provide structural integrity. These posts may also be used for electrical connectivity between the boards. The main drawback to this technique however, is that the posts pass directly through apertures within the boards, taking up valuable real estate within the module. Further, this structure does not include test points useful in testing the module at the manufacturing stage.
Another prior art technique for interconnecting circuit boards in a variety of modules, involves the use of connector rods attached to cutout grooves in the boards. The rods are mounted perpendicularly between two boards to form bridges. The rods fit into the cutout grooves and are soldered into place. These rods provide structural integrity as well as electrical connectivity. In a camera module however, the use of this technique to include test pads at the solder joints or test pads that are electrically connected to the solder joints is not disclosed.
There are packaging techniques which use flex cables to connect circuit boards in an image reader module. The flex cables are connected to the outer edges of the boards then folded to make the boards parallel to each other for packaging. The main drawback to this technique is the amount of flex cable that is required, and the wear and tear that is imparted on the cables when they are folded over. Further, the cables do not provide any structural integrity to the boards. The structural support must be provided in other ways such as the housing or support posts. A further disadvantage is the space that the folded cable takes up in the module. With ever decreasing module sizes, this can be a significant drawback.
Therefore there is a need for a packaging technique which allows for the needed level of miniaturization required by the industry, while providing test points electrically connected to the circuit boards useful in the verification and product testing stages of the manufacturing process.